Transcript ENVIRONMENTAL ANALYSIS I. Solid Phase Extraction oil & grease – EPA method 1664 O & G : Summary   Definitions Liquid / Liquid Extraction methods  Solid Phase Extraction.

ENVIRONMENTAL
ANALYSIS
I. Solid Phase Extraction
oil & grease –
EPA method 1664
O & G : Summary


Definitions
Liquid / Liquid Extraction methods

Solid Phase Extraction methods

Optimizing SPE: Special O&G Tube
Definitions
The Samples
Surface and Saline Waters
Industrial and Domestic Aqueous
Wastes
Waste Water Sludge
Definitions (cont.)
The Analytes
HEM: n-Hexane Extractable Material
TPH (or SGT-HEM): Total Petroleum
Hydrocarbons = Silica Gel Treated HEM
(HEMs not adsorbed by silica gel)
Examples: non-volatile hydrocarbons, waxes,
soaps, vegetable oils, animal fats, greases.
L / L Extraction
Solvent: CCl4
Hungarian Standard MSZ 260/22-74
Solvent: Freon-113
ASTM Method 413.1
Montreal Protocol on Substances that
Deplete the Ozone Layer  phase out
the use of CFCs
Solvent: n-Hexane
EPA Method 1664
L / L Extraction of O & G
Na2SO4
Drying
Evaporation
Purge
pH ~2
Weigh
Re-dissolve
Evaporation
Purge
Silica Gel
Treatment
Weigh
Features of Method 1664
The solvent (n-Hexane) is lighter than water
repouring the water means more labour
Four QA/QC samples per analytical batch
- blank
- blank spike
- matrix spike
- ms duplicate
Solvent-related matrix interferences
see Table (next slide)
EPA CFC Replacement Study
(mg/L)
CFC L/L n-C6 L/L SPED
POTW
27
25
25
Pump manufacturing
350
330
350
Chemical manufacturing
9
<5
22
Meat processor
22
27
54
Packaging plant
14
23
25
EPA 1664 Criteria
EPA 1664: Performance-Based Method
Acceptance Criteria
MS / MSD
Recovery
RSD
HEM
79-114
18
SGT-HEM
66-114
24
Why SPE?

Reduce solvent usage

Eliminate emulsion problem

Reduce handling

Readily amenable to automation
O & G on ISOLUTE TPH
Sample: #2 Fuel Oil
HCl to pH=2,
MeOH wetting agent
1.
2.
3.
4.
5.
6.
Sample pre-treatment
Column solvation
Column pre-equilibrium
Sample application
Interference elution
Analyte elution
10 mL MeOH
10 mL water
One liter in 1/2 hour
10 mL water, 15 min N2
2 x 3 mL THF/nC6 1:1
Petroleum Hydrocarbon
Recoveries: ISOLUTE TPH
Conc
mg/L
20.0
120.0
% rec
vs std
90
94
104
93
89
93
88
92
93
89
90
88
Avg
Std
Dev
94
5
90
2
EPA Represention of O & G
Fractions
Formerly: #2 Fuel Oil or Wesson Oil
Currently: Hexadecane - non-polar...
CH3
(CH2)14
CH3
Stearic Acid - polar fraction
O
CH3
(CH2)16
C
OH
Selective Elution
Polar vs. Non-Polar Fractions
First: Non-polar solvent

Second: Mixed solvent

Non-polar
interactions
Polar and Nonpolar
interactions
Selective Elution (cont.)
Hexadecane
+ Stearic
Acid
Hexadecane
Hexane
Hexane / THF
Stearic Acid
Recoveries from Selective
Elution
20 ppm spike
(90% C16, 10% stearic
acid)
Hexadecane (TPH)
Stearic Acid
96%
113%
Extraction of EPA 1664
Standards at High
Concentrations



Stearic acid spike precipitates
from solution
Plugging of sample lines and
extraction cartridges
Low recoveries
Building a TPH / Total O & G
Column
Polyester
Depth Filter
Large Particle
Special Phase
Std. Particle
Special Phase
Silica
Frits
Polyester Depth Filter


Oil and Grease: Distributes grease to
prevent frit and cartridge plugging
Particulates: Distributes solids to
prevent packing from plugging
Loading Rate with Depth Filter
Avg Loading Time, min: 34
Loading Rate, mL/min : 30
(n = 7)
O & G on ISOLUTE O & G
HCl to pH=2,
MeOH wetting agent
(sample temperature?)
1. Sample pre-treatment
2. Column solvation
3. Column preequilibrium
4. Sample application
5. Interference elution
6. Analyte elution
10 mL MeOH
10 mL water, pH 2
1/2 liter in 15-30 min
10 mL water, 30 min N2
1st: 3 mL Hexane
2nd: 3 mL THF/nC6 1:1
Impact of Various Factors
Elution solvent: Hexane / THF
Wetting Agent: 1% Methanol
Sorbents: 1/2 g or 1 g ISOLUTE O&G
Bottle wash: 20 mL Acetone + 80 mL water
Recoveries for TPH / Total O&G
Spike, mg/L
Recovery, %
%Recovery
Total O & G
120
Hexadecane:
Stearic Acid:
92
104
98
60
Hexadecane:
Stearic Acid:
94
96
95
24
Hexadecane:
Stearic Acid:
88
102
95
12
Hexadecane:
Stearic Acid:
87
100
94